(a) Field of the Invention
The present invention relates to a method and apparatus for wireless location measurement.
(b) Description of the Related Art
Wireless location measurement is a technology of obtaining information about position, speed, or other characteristics of an object by using wireless communication.
Wireless location measurement methods include an AOA (angle of arrival) method using received angles, an RSSI (received signal strength indicator) method using received signal strength, a TOA (time of arrival) method using arrival time of radio waves, a TDOA (time difference of arrival) method using an arrival time difference between radio waves, a DSOA (delay spread of arrival) method using delay spread of radio waves, and so on. Among these wireless location measurement methods, location measurement using characteristics of a radio channel is used for a wireless location measurement apparatus to calculate a propagation delay tab profile and calculate the distance between a transmitter and a receiver using information contained in the propagation delay tab profile.
The propagation delay tab profile can be obtained using a correlator. The correlator estimates a radio channel in a time domain by using preambles included in a received superframe. For example, the wireless location measurement apparatus can measure a location by performing first synchronization using a primary preamble included in a received superframe and then second synchronization using a secondary preamble followed by the primary preamble. In this manner, the correlator measures a location using a limited number of preambles of a superframe, so the location measurement period is longer than the duration of the superframe (e.g., 20 ms). Moreover, if the correlator accumulates received signals to extract a propagation delay tab profile, a period of time that is a plurality of times longer than the superframe duration is required. Thus, the position of the wireless location measurement apparatus may change during this period of time. As a result, the accuracy of location measurement may be lowered. The aforementioned method of extracting a propagation delay tab profile using a correlator may affect the performance of the wireless location measurement apparatus since the location measurement period is long and the amount of correlation calculation is large because a limited number of preambles are used.